Certain high speed electronic cable terminals employ arrays of spring pins to contact pads or lands of a circuit board or integrated circuit under test, or to contact connections of an electronic device for a permanent connection. The spring pins are straight, elongated pins received in cylindrical sleeves, and which are axially biased by spring pressure to an extended position. All pins extend in the same direction, with all the pin tips in a common plane. Contact is made by aligning the terminal with the device being probed or contacted, and applying axial pressure to ensure contact by each pin with a minimum pressure. The range of motion of each pin accommodates contour variations in the device being contacted, and slight variations in the position of each pin.
For applications in which very high frequency signals are to be transmitted, the cable to which the terminal is connected may be formed of coaxial wires, each shielded to provide consistent performance and to prevent cross talk and other electronic interference. A terminal housing having a metal shield layer encloses the sleeves retaining the pins. One such particularly effective device is shown in U.S. Pat. No. 6,575,772 to Soubh, the disclosure of which is incorporated herein by reference. This prior art connector has proven effective at providing a high impedance/high frequency probe assembly with relatively small probe spacing. It is believed to be useful for frequencies as high as 5 GHz. However, while effective, this limitation prevents usage for higher frequency applications.
Other prior art embodiments have sought to provide a high-speed connector with a metal block having sleeved spring pins inserted and protruding beyond the periphery of the block. While adequate for some applications, these suffer from certain performance variations between different connectors. Signals are carried through sleeves that are insulated from the block, and ground signals are carried through sleeves that are connected to the block. The ohmic connection between a ground pin sleeve and the block normally occurs near the periphery of the block, because the sleeve has a slightly wider portion at its end adjacent to the aperture from which the spring pin emerges. Thus, a ground signal is conducted from the pin tip, down the length of the pin to the spring at the opposite end of the pin, which bears on the sleeve. The ground signal then passes along the sleeve in the reverse direction until it reaches the point of contact where the sleeve bulges and is press-fit within the block, after which the ground signal is conducted through the block in the original direction. However, if the pin makes contact with the sleeve near the sleeve aperture, or if the sleeve makes contact with the block well away from the aperture, the ground signal path is substantially shortened, avoiding the zigzagging path described above in the nominal case. This possibility can lead to inconsistent performance between ground conductors, impairing results.